1. Field of the Invention
The present invention pertains to the field of disk drives. In particular, embodiments of the present invention relate to methods and systems for assembling disk drives.
2. Description of the Related Art
During assembly of a disk drive, a Head Stack Assembly (HSA) must be picked from a HSA shipping tray and placed into a Head Disk Assembly (HDA) or an intermediate fixture. Conventionally, this pick and place operation is carried out by manually picking up a HSA from a HSA shipping tray and manually placing the picked up HSA into the HDA or the intermediate fixture. Even through the workers are grounded, the incidence of damage to the HSA through electrostatic discharge (ESD), although reduced, is not eliminated.
The HSA typically includes a flex circuit that electrically couples the Flex Circuit Connector (FCC) to the tail stack of the HSA. The flex circuit may be formed of an electrically insulating material in which a plurality of electrical traces is embedded. Although the flex circuit is typically formed of relatively tough polyimide (sold by DuPont, Inc. under the trade name Capton®, for example), it remains susceptible to scratches and abrasion damage. Such scratches may occur when the tail stack of the HSA contacts the flex circuit during shipment or when the HSA is placed into the disk drive during assembly. To reduce the incidence of such scratches, head stack assemblies are typically shipped in a HSA shipping tray in a configuration in which the flex circuit is held away from the tail stack of the HSA.
FIG. 1 shows a typical HSA shipping tray 102 in which HSAs are shipped. As shown, the HSA shipping tray 102 may be injection molded or may be a relatively inexpensive thermo-formed plastic tray that defines a plurality of recesses 104 shaped so as to receive a single HSA. For clarity of illustration only a single HSA 106 is shown received within one of the recesses 104. As shown, the HSA 106 may include a FCC 110 and a flex circuit 108. As shown, to avoid damaging the flex circuit 108 during shipping, the recesses within the HSA shipping tray are configured so as to keep the FCC 110 away from the actuator arms and the actuator body of the actuator assembly of the HSA 106.
FIG. 2 is a plan view of a portion of a HSA shipping tray 102, showing a HSA 106 fitted within one of the recesses 104 therein. As shown, the FCC 110 may be disposed within the HSA shipping tray 102 such that the flex circuit 108 is disposed apart from the tail stack 202 of the HSA 106. A distance 204 between the flex circuit 108 and tail stack 202 is chosen to be sufficiently large so as to significantly reduce the incidence of abrasion damage to the flex circuit 108—that is to prevent the tail stack 202 or other structures of the HSA 106 from coming into contact with the flex circuit 108 during both the shipping and assembly processes.
However, the HSAs, while shipped in a configuration that reduces the incidence of potentially yield-reducing abrasions to the flex circuit 108, are typically coupled to the base of a disk drive in a different configuration. FIG. 3 shows a head stack assembly 106 in this “coupling” configuration, enabling it to be coupled to the base 302 of a disk drive. When coupled to the base 302, the HSA 106 is often placed in a configuration in which the flex circuit 108 is comparatively closer to the actuator arms and actuator body of the actuator assembly of HSA 106 than it is when the HSA 106 is disposed within the HSA shipping tray 102. Solely to aid in visualizing the difference between the configuration of the HSA 106 when fitted within the HSA shipping tray 102 and the configuration of the HSA 106 when coupled to the disk drive base 302, the flex circuit 108 appears twice in FIG. 3. The flex circuit 108 shown in dashed lines illustrates the relative position of the flex circuit 108 when the HSA 106 is disposed within the HSA shipping tray 102. In contrast, the flex circuit 108 shown in solid lines represents the position thereof when the HSA 106 is placed within the disk drive base 302. As may be seen from this composite view, the flex circuit 108 is moved closer to the actuator arms and actuator body of the HSA 106 to place it into the disk drive base 302.
From the foregoing, it is apparent that the FCC 110 must be somehow articulated relative to the actuator assembly from its first configuration in the HSA shipping tray 102 to a second configuration suitable for placing it into a disk drive base 302. Manually picking up the HSAs from the HSA shipping tray does not completely obviate the risk of scratching the flex circuit. Indeed, in some shipping trays, the configuration of the HSA 106 in the shipping tray 102 is such that a person must pick up the HSA 106 by placing his or her fingertips within 0.5 inches of the tail stack 202. Under such circumstances, even the smallest human error can produce damage. What are needed, therefore, are methods and systems for effectively assembling a portion of a disk drive.